The long-term objective of this application is to improve prostate cancer care for elderly patients. Although prostate cancer is common, outcomes data specific for elderly patients (aged 75 years or older) are sparse. In the past decade, the use of primary androgen deprivation therapy (PADT) for localized prostate cancer has increased by more than 25% among elderly men, perhaps because it is often perceived as safer than the alternatives of surgery or radiation. Disturbingly, among elderly patients the risk of being hospitalized for fractures within five year of cancer diagnosis (20%) increased by more than 50% after 5 years of PADT use compared with patients without any androgen deprivation. Disease-specific mortality and serious cancer- related complications;however, are similar between long-term and short-term PADT users. Because of the concerns about the potential side effects of PADT, the Prostate Cancer Progress Review Groups has identified assessment of PADT as a top priority in the current prostate cancer research plan. The primary objectives of the study will be to define the prognosis of elderly patients with localized prostate cancer, in term of fractures, overall and disease-specific survival, and serious-cancer related complications, following PADT and conservative management. Furthermore, this proposed study will assess these outcomes as a function of the duration of PADT exposure and quantify the excess risk associated with PADT use. This population-based study will use the SEER-Medicare linked data to identify eligible patients diagnosed in 1992-2002. Because of its large sample size (about 38,000 men with up to 12 years of follow-up), this study will have ample statistical power. The data will be analyzed utilizing modern methods designed to minimize biases (e.g., propensity scores, prospective eligibility criteria, multivariate analysis). The findings of this study will be important for informed decision making, planning for future trials, and developing strategies to improve the quality of care. Lay Description-About 69,000 new prostate cancer cases are diagnosed among men over age 75 each year. This study is to provide the probabilities of various clinical outcomes following two commonly used treatment options: deferred treatment and hormonal therapy. The findings of this study will provide benchmark references to help elderly patients weigh the potential risks and benefits of alternative approaches and to facilitate treatment decision-making.